1. Field of the Invention
The present invention relates to a novel 8-oxoprotoberberine derivative or a pharmaceutically acceptable salt thereof, a preparation method thereof, and a pharmaceutical composition for preventing or treating diseases associated with the activity of NFAT5 containing the same as an active ingredient.
2. Description of the Related Art
Autoimmunity is a kind of immune response in human body, in which the body recognizes its own organ or tissue as an antigen invading from the outside so that it causes an immune response against it. Basically, the immune response is a system to defend human body against a foreign antigen such as a pathogen. However, when human body attacks its own organ or tissue because of autoimmunity, various diseases can be developed. Rheumatoid arthritis, systemic scleroderma, lupus erythematosus, atopic dermatitis, Behcet's disease, Sjogren's syndrome, multiple sclerosis, and Graves' hyperthyroidism are the examples of auto-immune disease.
Rheumatoid arthritis is an auto-immune disease that causes chronic and systemic inflammation in many tissues and organs. In this disease, the flexible synovial is mainly attacked to give pain and be transformed. If it is not properly treated, functions and motility will be damaged or lost. As the disease progresses, the joint is swollen owing to a huge amount of synovial fluid, the fibrous tissue (pannus) in the synovial is developed, the articular cartilage is destroyed, and inflammation is caused in ankylosis, lung, pericardium, pleura, and sclera. However, the cause of autoimmunity that causes rheumatoid arthritis has not been explained yet. Approximately 0.6% of adult population in USA is suffering from rheumatoid arthritis and the rate of female patient is 2˜3 times higher than that of male patient (Non-Patent Reference 1).
The treatment of rheumatoid arthritis depends on the nonpharmacologic method such as physical therapy, orthoses and occupational therapy, and the pharmacologic method such as nutrition therapy, pain killer administration and anti-inflammatory drug administration. For the pharmacologic treatment, non-steroidal anti-inflammatory drug (NSAID) or disease-modified anti-rheumatic drug (DMARD) can be used. The said non-steroidal anti-inflammatory drug is effective by inhibiting the synthesis of prostaglandin by suppressing the enzyme activity of cyclooxygenase 2 (COX2) that is an important inflammation mediator, which is exemplified by diclofenac, piroxicam, indomethacin, meloxicam, celecoxib, rofecoxib, or lumiracoxib. However, these drugs cannot stop the progress of joint damage. The anti-rheumatoid drugs that can stop or delay the progress of the disease are exemplified by methotrexate, leflunomide, hydroxychloroquine, sulfasalazine, azathioprine, cyclophosphamide, and cyclosporine A. Anti-TNF-α antibody drug is also included in the category. As a low molecule drug, the JAK3 inhibitor Xeljanz (Tofacitinib, Pfizer) was first introduced in the market in 2012. Nevertheless, there are still numbers of non-reactive patients who do not respond to the conventional drugs, suggesting that unmet medical needs are still high, so that it is highly requested to develop a novel drug with a novel mechanism.
NFAT (nuclear factor of activated T cells) is a protein existing in cell membrane, which is activated by the Ca2+ mobilization coupled cell surface receptor. NEAT protein is dephosphorylated by calcineurin that is the phosphatase activated by Ca2+. The dephosphorylated NFAT migrates into the nucleus and induce the transcription of various cytokine genes including IL-2 necessary for the activation of T-cells.
In particular, NFAT5 (nuclear factor of activated T cells 5) is also called TonEBP (tonicity enhancer binding protein), OREBP, NFATL1, or NFATz. NFAT5 is the longest transcription regulator and displays a clear structural and functional difference from other transcription regulators {NFAT1 (NFATp, NFATc2), NFAT2 (NFATc, NFATc1), NFAT3 (NFATc4), NFAT4 (NFATx, NFATc3)} (Non-Patent References 2 and 3). NFAT5 is composed of approximately 1,500 amino acids and is expressed in almost every tissue, particularly displays a high expression in the kidney, lung, pituitary gland, placenta, testis, and thymus of a fetus characterized by active metabolism and aggressive development (Non-Patent Reference 4). NFAT5 does not have a calcineurin domain, suggesting that it is not directly affected by the calcium concentration. In a hypertonic solution with the increased osmotic pressure, NFAT5 is activated by osmostress and maintains homeostasis. The NFAT5 activated in T cells binds to CD24 promoter to increase the transcription of CD24, by which the amplification of T cells is induced.
ROS (reactive oxygen species) and p38 MAPK are the factors associated with NFAT5 upstream. It was previously reported that ROS is associated with the activation of NFAT5 induced by TLR (Toll-like receptor) (Non-Patent Reference 5). NO (nitric oxide), a member of ROS family, is generated by iNOS (inducible nitric oxide synthase). NO induced by iNOS plays an important role in many diseases, particularly in inflammation response. The expression of iNOS is characteristically shown in many diseases, according to the previous report (Non-Patent Reference 6).
It was recently reported that NFAT5 is highly expressed in synovial fluid of patients with rheumatoid arthritis, one of auto-immune diseases, and increases the secretion of inflammatory cytokines such as IL-1β and TNF-α (Non-Patent Reference 7). It was observed that the cell proliferation, angiogenesis, or cell migration was significantly reduced in NFAT5 knocked-down synovial cells or vascular cells (HUVEC) by using siRNA. In the NFAT5(+/−) mouse, inflammation in the joint was significantly reduced. Therefore, it is suggested that a compound that can inhibit the activity of NFAT5 can be a promising candidate for the novel treating agent for improving rheumatoid arthritis.
Berberine is a quaternary ammonium salt of isoquinoline alkaloid, which is known as an herbal medicine included in golden thread. It has been reported that berberine has the anti-cancer, anti-obesity, and anti-diabetic effect. Berberine is the active ingredient of the natural digestive ‘Jungrowhan’ which has the activities of inhibiting enterobacteria, anticonvulsive/sedative, preventing atherosclerosis, anti-inflammatory, choleretic, and promoting the secretion of pancreatic juice.
It was observed that protoberberine, a berberine derivative wherein various substituents are inserted in the 13th site of berberine with displaying remarkably improved NFAT5 inhibiting effect and COX enzyme inhibiting effect, was excellent in inhibiting inflammation in arthritis animal model. However, the said protoberberine has a low solubility so that it is not absorbed well through oral-administration, suggesting that it is hard to be developed as an oral-preparation.
The present inventors were fully aware of that a novel drug with a novel mechanism is necessary to cope with the drug-resistance since arthritis or auto-immune disease is the kind of disease that requires a long-term treatment and also recognized that an oral-preparation is preferred over an injection. Therefore, in the course of study to develop a compound that has NFAT5 inhibiting effect and can be orally administrated, the present inventors confirmed that the novel 8-oxoprotoberberine derivative has an excellent NFAT5 inhibiting effect and can be useful as an anti-rheumatoid arthritis agent suitable for the oral-administration, leading to the completion of the invention.